To force trailing zeros in an Excel cell, follow these steps:

1. Select the cells that you want to format.
2. Right-click on the selected cells and choose "Format Cells" from the context menu.
3. In the "Format Cells" dialog box, click on the "Number" tab.
4. In the "Category" list, select "Text".
5. Click "OK" to apply the formatting.

To add trailing zeros to numbers that have already been entered, use the "Custom" number format:

1. Select the cells that you want to format.
2. Right-click on the selected cells and choose "Format Cells" from the context menu.
3. In the "Format Cells" dialog box, click on the "Number" tab.
4. In the "Category" list, select "Custom".
5. In the "Type" field, enter the following format code:
   Formula:

   0.00000# 

6. Click "OK" to apply the formatting.

This will add trailing zeros to any numbers that you enter in the selected cells.